The present invention relates to a blasting works recovery system, comprising a space for receiving the blast material below a perforated floor of the blasting works, and suction ducts for directing the blast material from the space below the floor to a classifier with the help of a blower. The recovery system includes at least one elongated, substantially horizontal, chute opening upwards with two side walls fitted into the said space, and elongated cover element with two elongated free side edges arranged over the chute, the chute and the cover element forming between them a discharge channel for the blast material. The system comprises pneumatic cylinders for moving the cover element in vertical direction between a lower and a raised position so that in the lower position, the side edges of the cover element engage the side walls of the chute and, in the raised position, the side edges of the cover element are at a distance from the chute side walls, thus forming two elongated suction gaps for leading the blast material to the discharge channel.
A recovery system for blasting works on the described type is known from the patent publication FI 84891. In this known solution, several, e.g. 30 pneumatic cylinders are needed to move the cover elements in blasting works of 20 meters long with five adjacent chutes. Additionally, the said patent publication proposes that only one cover element at a time is raised.
The object of the invention is to further improve the blasting works recovery system of the said patent publication, to avoid its drawbacks and to produce a reliable and cost-effective recovery system for blasting works.
These objects can be achieved by a blasting works recovery system in accordance with the present invention, the principal features of which will be evident from the enclosed claims.
It is thus characteristic of the blasting works recovery system of the present invention that it further comprises springs that cooperate with the pneumatic cylinders for facilitating the movement of the cover element. The solution of the invention makes it possible to substantially reduce the number of pneumatic cylinders required for the cover elements, which in its part reduces the costs of the blasting works recovery system.
The recovery system of the present invention advantageously comprises two or more parallel chutes opening upwards, and cover elements fitted over the chutes. The cover elements are advantageously arranged to move simultaneously with the help of the pneumatic cylinders and springs.
The one end of the springs is attached to the cover element and the other end to a fixed structure above the cover element, for example to a protective plate protecting the pneumatic cylinders. The springs may be attached in pairs to both sides of each pneumatic cylinder. The said springs are preferably spiral springs.
According to an advantageous embodiment, a filter is placed between the classifier and blower for filtering dusty air coming from the classifier. A suction chute of the before mentioned type, but shorter, may be arranged below the said filter, along which the waste material is transferred from the filter to a cyclone in which the waste material is separated, and clean air is directed to the blower.
In accordance with the invention, only one blower is required for the handling of the blast material, ventilation in the blast chamber, removal of dust and transfer of waste in the blasting works.
The recovery system of the invention may also comprise separate classifiers for different blast materials, such as sand and steel. This may be realized by equipping the suction ducts with a distribution branch with one branch leading to the first classifier and another to the second classifier.
The recovery system of the present invention makes it possible to construct the blasting works as one or several units which may be moved from one place to another and, for example, to use them when repairing structures under bridges.